[Deficit: the value and difficulty of defining the primary or secondary character of observed symptoms].

Since early descriptions of schizophrenia, heterogeneousness of clinical forms is one of the most typical figure of the disease. Nowadays authors perceived the necessity for patients to gather in groups in the most homogeneous way. First, different clinical effects have been noticed among schizophrenic patients with neuroleptics in function of their type or their dose. Then dichotomic concepts between positive and negative forms of schizophrenia succeeded one another. Several scales for negative symptoms of schizophrenia have been used to test the antideficit effect of different doses of neuroleptic agents. But these punctual evaluations cannot confirm primary nature of these symptoms, not derived from positive, depressive, anxious symptoms or secondary symptoms of neuroleptic treatment (as akinesia). Carpenter et al. defined the concept of deficit syndrome in schizophrenia, which can be evaluated with the SDS (Schedule for the Deficit Syndrome, Kirkpatrick et al., 1989). This classification of patients showed certain particularities: clinical, neurologic and biological ones, which seemed to confirm the initial hypothesis of homogeneousness of deficit syndrome in schizophrenia. The relevance of this concept forecasts a very promising future to research in the area of schizophrenia, with therapeutic and evolutive implications.